Back in my wedgie days, I commuted on a '73 Raleigh International (pretty lugged 531 frame, mostly campy) that I adulterated into a commuter bike. I changed to a split shift to give me drag racing gears, randonneur bars, short Weinmann sidepulls. Added fenders, converted to clinchers (27x1 1/8 front, 27 x 1 1.4 rear - I'm 220#). Of late, I've replaced the wheels with 700Cx28s.
But that's not what I came to talk about.
I want to convert this bike into an urban assault vehicle - the kind of bike I'd ride from the Battery to the GW Bridge, or up Michigan Avenue, or Younge Street... My plan is to use a Sturmey Archer AW (alloy hub shell) with two speed derailleur on it, single sprocket the front, very narrow flat alloy bars, replace the Record pedals with SPDs. Put on the fattest 700Cs that fit the frame, probably 32s, for the occasional pothole jump. I might even strip/sandblast off the three coats of marine epoxy paint and replicate the original Chartreuse - or paint it flat black to reduce the theft value.
It needs to be light enough to accelerate well and carry onto the subway, yet strong enough to withstand the bad streets.